Device and method to reduce power amplifier power consumption

Abstract

A wireless device and method of power consumption reduction are generally described herein. The wireless device may map a plurality of data symbols to sub-carriers for an orthogonal frequency division multiplexing (OFDM) transmission. The wireless device may divide the plurality of data symbols into first and second groups of data symbols. The wireless device may generate a first OFDM signal from the first group of data symbols for amplification by a first power amplifier (PA). The wireless device may generate a second OFDM signal from the second group of data symbols for amplification by a second PA. The data symbols of the first and second groups may be selected to provide a PAPR of the first OFDM signal that is lower than a PAPR of a composite OFDM signal based on the plurality of data symbols.

What is claimed is: 
     
       1. An apparatus of a wireless device, the apparatus comprising:
 memory; and 
 processing circuitry, the processing circuitry configured to:
 map a plurality of data symbols to sub-carriers for a multiplexed transmission; 
 generate a composite multiplexed signal from the plurality of data symbols; 
 clip the composite multiplexed signal based on a predetermined threshold; 
 determine a difference signal between the composite multiplexed signal and the clipped composite multiplexed signal; 
 determine sub-carrier magnitudes of the difference signal based on a Fourier Transform (FT) of the difference signal; 
 divide the plurality of data symbols into a first group of data symbols and a second group of data symbols based on the sub-carrier magnitudes of the difference signal; 
 generate a first multiplexed signal from the first group of data symbols for amplification by a first power amplifier; and 
 generate a second multiplexed signal from the second group of data symbols for amplification by a second power amplifier, wherein selection of the first and second groups of data symbols from the plurality of data symbols is made to provide a lower power ratio of the first multiplexed signal than the composite multiplexed signal, the composite multiplexed signal generated from data symbols of both the first group and the second group. 
 
 
     
     
       2. The apparatus according to  claim 1 , wherein:
 the multiplexed transmission is an orthogonal frequency division multiplexing (OFDM) transmission, 
 the first multiplexed signal is a first OFDM signal, the second multiplexed signal is a second OFDM signal, and the composite multiplexed signal is a composite OFDM signal, and 
 the power ratio is a peak-to-average power ratio (PAPR). 
 
     
     
       3. The apparatus according to  claim 1 , wherein:
 the multiplexed transmission is a single-carrier frequency division multiple access (SC-FDMA) transmission, 
 the first multiplexed signal is a first SC-FDMA signal, the second multiplexed signal is a second SC-FDMA signal, and the composite multiplexed signal is a composite SC-FDMA signal, and 
 the power ratio is a peak-to-average power ratio (PAPR). 
 
     
     
       4. The apparatus according to  claim 1 , wherein:
 the second group of data symbols includes a predetermined number of the plurality of data symbols, 
 the first group of data symbols includes data symbols different from the second group, 
 the plurality of data symbols of the first group are mapped to a first group of sub-carriers and the plurality of data symbols of the second group are mapped to a second group of sub-carriers, 
 wherein the sub-carrier magnitudes of the second group of sub-carriers are higher than the sub-carrier magnitudes of the first group of sub-carriers. 
 
     
     
       5. The apparatus according to  claim 1 , wherein dividing the plurality of data symbols into the first and second groups of data symbols provides variable sizes of the first and second groups. 
     
     
       6. An apparatus of a wireless device, the apparatus comprising:
 memory; and 
 processing circuitry, the processing circuitry configured to:
 map a plurality of data symbols to sub-carriers for a multiplexed transmission; 
 generate a composite multiplexed signal from the plurality of data symbols; 
 divide the plurality of data symbols into a first group of data symbols and a second group of data symbols based at least partly on the composite multiplexed signal; 
 generate a first multiplexed signal from the first group of data symbols for amplification by a first power amplifier; and 
 generate a second multiplexed signal from the second group of data symbols for amplification by a second power amplifier, wherein the first and second groups of data symbols provide a lower power ratio of the first multiplexed signal than the composite multiplexed signal, the processing circuitry further configured to:
 initialize the second group of data symbols to an empty group; 
 initialize the first group of data symbols to include the plurality of data symbols; 
 for a predetermined number of iterations:
 generate a first set of sub-carrier values, wherein values of the sub-carriers mapped to the plurality of data symbols of the second group are set to zero and values of the sub-carriers mapped to the plurality of data symbols of the first group are set to the corresponding data symbols; 
 generate a first multiplexed signal based on the first set of sub-carrier values; 
 clip the first multiplexed signal based on a predetermined threshold; 
 determine a difference signal between the first multiplexed signal and the clipped first multiplexed signal; 
 generate a second set of sub-carrier values based on a Fourier Transform (FT) of the difference signal; 
 determine a particular data symbol for inclusion in the second group based at least partly on the second set of sub-carrier values; and 
 include the determined data symbol in the second group and exclude the determined data symbol from the first group. 
 
 
 
 
     
     
       7. The apparatus according to  claim 6 , the processing circuitry further configured to:
 for the predetermined number of iterations:
 determine a candidate group of data symbols based on magnitudes of the second set of sub-carrier values; 
 for each data symbol of the candidate group:
 determine a third set of sub-carrier values, wherein the value of the sub-carrier mapped to the data symbol of the candidate group is set to zero, and wherein values of other sub-carriers are set to corresponding values of the first set of sub-carrier values; 
 determine a candidate multiplexed signal based on an inverse FT of the third set of sub-carrier values; and 
 determine a peak power metric for the data symbol of the candidate group based on a maximum magnitude of the candidate multiplexed signal; and 
 
 determine the particular data symbol for inclusion in the second group as the data symbol of the candidate group of minimum peak power metric. 
 
 
     
     
       8. The apparatus according to  claim 7 , the processing circuitry further configured to:
 for at least a portion of the iterations:
 determine multiple data symbols for inclusion in the second group based at least partly on the second set of sub-carrier values; and 
 include the determined data symbols in the second group and exclude the determined data symbols from the first group. 
 
 
     
     
       9. An apparatus of a wireless device, the apparatus comprising:
 memory; and 
 processing circuitry, the processing circuitry configured to:
 map a plurality of data symbols to sub-carriers for a multiplexed transmission; 
 generate a composite multiplexed signal from the plurality of data symbols; 
 divide the plurality of data symbols into a first group of data symbols and a second group of data symbols based at least partly on the composite multiplexed signal; 
 generate a first multiplexed signal from the first group of data symbols for amplification by a first power amplifier; and 
 generate a second multiplexed signal from the second group of data symbols for amplification by a second power amplifier, wherein the first and second groups of data symbols provide a lower power ratio of the first multiplexed signal than the composite multiplexed signal, the processing circuitry further configured to:
 map the plurality of data symbols to the sub-carriers in accordance with a predetermined mapping; 
 set values of the sub-carriers to which the data symbols of the second group are mapped to zero to generate the first multiplexed signal; and 
 set values of the sub-carriers to which the data symbols of the first group are mapped to zero to generate the second multiplexed signal. 
 
 
 
     
     
       10. The apparatus according to  claim 1 , wherein:
 the division of the data symbols into the first and second groups reduces a sum of power consumptions of the first power amplifier and the second power amplifier in comparison to a power consumption based on amplification of the composite multiplexed signal. 
 
     
     
       11. The apparatus according to  claim 1 , wherein:
 the plurality of data symbols is a first plurality of data symbols divided in accordance with a first division, and the multiplexed transmission is a first multiplexed transmission of a first multiplexed symbol period, 
 the processing circuitry is further configured to:
 map a second plurality of data symbols to the sub-carriers for a second multiplexed transmission during a second multiplexed symbol period; and 
 divide the second data symbols in accordance with a second division different from the first division. 
 
 
     
     
       12. An apparatus of a wireless device, the apparatus comprising:
 memory; and 
 processing circuitry, the processing circuitry configured to:
 map a plurality of data symbols to sub-carriers for a multiplexed transmission; 
 generate a composite multiplexed signal from the plurality of data symbols; 
 divide the plurality of data symbols into a first group of data symbols and a second group of data symbols based at least partly on the composite multiplexed signal; 
 generate a first multiplexed signal from the first group of data symbols for amplification by a first power amplifier; and 
 generate a second multiplexed signal from the second group of data symbols for amplification by a second power amplifier, wherein the first and second groups of data symbols provide a lower power ratio of the first multiplexed signal than the composite multiplexed signal, the processing circuitry further configured to:
 when a modulation size of the data symbols is greater than or equal to a modulation size threshold:
 divide the plurality of data symbols into the first and second groups of data symbols; 
 generate the first multiplexed signal for the amplification by the first power amplifier; and 
 generate the second multiplexed signal for the amplification by the second power amplifier, and 
 
 when the modulation size of the data symbols is less than the modulation size threshold:
 generate the composite multiplexed signal for amplification by the second power amplifier. 
 
 
 
 
     
     
       13. The apparatus according to  claim 1 , wherein the first and second multiplexed signals are baseband signals generated for the amplifications by the first and second power amplifiers in a radio frequency (RF) range. 
     
     
       14. The apparatus according to  claim 1 , wherein the apparatus further comprises the first power amplifier, the second power amplifier, and a combiner to combine output signals from the first and second power amplifier. 
     
     
       15. The apparatus according to  claim 1 , wherein the processing circuitry comprises a baseband processor to map the plurality of data symbols, divide the plurality of data symbols, and generate the first multiplexed signal, the second multiplexed signal, and the composite multiplexed signal. 
     
     
       16. A non-transitory computer-readable storage medium that stores instructions for execution by one or more processors to perform operations to generate signals for one or more power amplifiers, the operations to configure the one or more processors to:
 map a plurality of data symbols to sub-carriers for an orthogonal frequency division multiplexing (OFDM) transmission; 
 generate a composite OFDM signal based on the plurality of data symbols; 
 clip the composite OFDM signal in accordance with a predetermined threshold; 
 determine a difference signal between the composite OFDM signal and the clipped composite OFDM signal; 
 determine sub-carrier magnitudes of the difference signal based on a Fourier Transform (FT) of the difference signal; and 
 based on the sub-carrier magnitudes of the difference signal, divide the plurality of data symbols into a first group of data symbols and a second group of data symbols for generation of a first OFDM signal for amplification by a first power amplifier and a second OFDM signal for amplification by a second power amplifier, wherein selection of the first and second groups of data symbols from the plurality of data symbols is made in accordance with a peak-to-average power ratio (PAPR) criterion in which a PAPR of the first OFDM signal is lower than a PAPR of the second OFDM signal and is lower than a PAPR of the composite OFDM signal. 
 
     
     
       17. The non-transitory computer-readable storage medium according to  claim 16 , the operations to further configure the one or more processors to:
 divide the plurality of data symbols into the first and second groups of data symbols, such that dividing the plurality of data symbols into the first and second groups of data symbols reduces a combined power consumption of the first and second power amplifiers in comparison to a reference power consumption for amplification of the composite OFDM signal. 
 
     
     
       18. The non-transitory computer-readable storage medium according to  claim 16 , the operations to further configure the one or more processors to select, for the second group of data symbols, a predetermined number of the plurality of data symbols for which the sub-carrier magnitudes are in a highest range of the sub-carrier magnitudes sorted in an ascending order. 
     
     
       19. A method of signal generation, the method comprising:
 mapping a plurality of data symbols to sub-carriers for an orthogonal frequency division multiplexing (OFDM) transmission; 
 generating a composite OFDM signal from the plurality of data symbols; 
 clipping the composite OFDM signal based on a predetermined threshold; 
 determining a difference signal between the composite OFDM signal and the clipped composite OFDM signal; 
 determining sub-carrier magnitudes of the difference signal based on a Fourier Transform (FT) of the difference signal; and 
 dividing the data symbols into the first and second groups of data symbols based at least partly on the sub-carrier magnitudes of the difference signal; 
 generating a first OFDM signal from the first group of data symbols for amplification by a first power amplifier; and 
 generating a second OFDM signal from the second group of data symbols for amplification by a second power amplifier, 
 wherein the data symbols of the first and second groups are selected to provide a lower power ratio of the first OFDM signal than the second OFDM signal and a lower power ratio of the first OFDM signal than a reference power ratio of a composite OFDM signal based on the first and second groups of data symbols. 
 
     
     
       20. The method according to  claim 19 , wherein the power ratio is a peak-to-average power ratio (PAPR). 
     
     
       21. The method according to  claim 20 , further comprising:
 for multiple candidate divisions of the data symbols:
 dividing the plurality of data symbols into a candidate first group of data symbols and a candidate second group of data symbols; and 
 determining a candidate first PAPR of a candidate first OFDM signal based on the candidate first group of data symbols; and 
 
 selecting the first and second groups of data symbols as the candidate first and second groups of data symbols for which the candidate first PAPR is minimized.